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RAD201 Exam 2
| What is Radiation Biology? | Branch of biology concerned with the effects of ionizing radiation on living systems |
| What does Radiation Biology include? | Sequence of events occurring after the absorption of energy from ionizing radiation, action of the living system to compensate for the consequences of this energy assimilation, and injury to the living system that may be produced |
| What is Ionizing Radiation? | Damages living systems by ionizing the atoms comprising the molecular structure of these systems |
| Biologic damage begins with the ionization produced by various types of radiation such as what? | X-rays, gamma rays, alpha particles, beta particles, and protons |
| True or False: Ionized atoms will not bond properly in molecules | True |
| Among the different types of radiation, what varies among them? | Charge, mass, and energy |
| What do these factors attribute to? | Determine the extent to which different radiation modalities transfer energy into biologic tissue |
| What are the three concepts that help us to understand the way ionizing radiation causes injury and how the effects may vary in biologic tissue? | Linear energy transfer, Relative biologic effectiveness, and Oxygen enhancement ratio |
| What is Linear Energy Transfer (LET)? | The average energy deposited per unit length of track by ionizing radiation as it passes through and interacts with a medium along its path |
| Why is LET important? | Assessing potential tissue and organ damage from exposure to ionizing radiation |
| What are the categories according to LET? | Low-linear energy transfer radiation and High-linear energy transfer radiation |
| What are examples of low-LET radiation? | Gamma rays and x-rays |
| What are examples of high-LET radiation? | Alpha particles, ions of heavy nuclei, charged particles released from interactions between neutrons and atoms, and low-energy neutrons |
| What is the relative biologic effectiveness (RBE)? | The relative capabilities of radiation with differing LETs to produce a particular biologic reaction |
| What does the RBE ratio entail? | The dose of a reference radiation to the dose of radiation of the type in question that is necessary to produce the same biologic reaction in a given environment. It is produced by a dose of the test radiation delivered under the same conditions. |
| What is the RBE formula? | RBE = Dose in Gy from 250-kVp x-rays (reference radiation) / Dose in Gy of test radiation |
| What is the Oxygen Enhancement Ratio (OER)? | Ratio of the radiation dose required to cause a particular biologic response of cells or organisms in any oxygen-deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions |
| True or False: In general, x-rays and gamma rays have an OER of about 3.0 when radiation dose is high | True |
| True or False: OER may be less (approximately 2.0) when radiation doses are below 2 Gyt | True |
| What is the formula/ratio for OER? | OER = Radiation dose required to cause biologic response without O2 / Radiation dose required to cause biologic response with O2 |
| What are the three levels observed for biologic damage from ionizing radiation? | Biologic damage stemming from exposure to ionizing radiation is observed on three levels: molecular, cellular, and organic systems |
| True or False: any visible radiation-induced injuries of living systems at the cellular or organic level always begin with damage at the molecular level | True |
| True or False: Molecular damage results in the formation of structurally changed molecules that may impair cellular functioning | True |
| True or False: Since energy from ionizing radiation can alter a human cell's molecules, such exposure may disturb the cell's chemical balance and the way it operates. | True |
| True or False: If a sufficient quantity of somatic cells are affected, entire body processes will not be disrupted | False; it will be disrupted |
| True or False: If radiation damages the germ cells, the damage may not be on to future generations in the form of genetic mutations | False; it may be passed on to future generations in the form of genetic mutations |
| What are the two classifications of ionizing radiation interaction on a cell? | Direct action (in DNA) and Indirect action (in H20) |
| True or False: Since the human body is 80% water and less than 1% DNA, all effect of low-LET irradiation in a living cell result from indirect action | True |
| What does radiolysis of water include? | Ionization of water molecules, production of free radicals, production of undesirable chemical reactions and biologic damage, production of cell-damaging structures, and organic free radical formation |
| What is a single-strand break? | Ionizing radiation interacts with DNA macromolecule, transfers energy, and ruptures one of the molecule's chemical bonds, possibly severing one of the sugar-phosphate chain side rails |
| What can reverse the single-strand break? | Repair enzymes |
| What is a double-strand break? | More exposure of the affected DNA macromolecule to ionizing radiation which |
| Can double-strand breaks be repaired? | They are able to but are not repaired as easily as single-strand breaks |
| True or False: If repair does not take place, further separation may occur in the DNA chains, threatening the life of the cell | True |
| When dose double-strand occur? | More commonly with densely ionizing (high-LET) radiation |
| What is rung of DNA? | Cleaved or broken chromosome with each new portion containing an unequal amount of genetic material. |
| True or False: If damaged chromosome divides, each new daughter cell will receive an incorrect amount of genetic material culminating in the death or impaired functioning of the new daughter cell | True |
| What is mutation? | Interactions of ionizing radiation with DNA molecules may cause the loss of or change in a nitrogenous base in the DNA chain. Direct consequence of this damage is an alteration of the base sequence. |
| What are covalent cross-links? | Chemical unions created between atoms by the single sharing of one of more pairs of electrons. Initiated by high-energy radiation. |
| What are the effects of ionizing radiation on chromosomes? | Large-scale structural changes in a chromosome produced by ionizing radiation may be as grave for the cell as are radiation-induced changes in DNA |
| What are radiation-induced chromosome breaks in somatic and reproductive cells? | Chromosomal fragments, chromosome anomalies (chromosome aberrations and chromatid aberrations). and structural changes in biologic tissue |
| What are some consequences to the cell from structural changes within the nucleus? | Restitution, Deletion, Broken-end rearrangement producing grossly misshapen chromosomes, and Broken-end rearrangement without visible damage to the chromatids |
| What is target theory? | A master or key molecule that maintains normal cell function and believed to be present in every cell. It is necessary for cell survival and used to explain cell death and nonfatal cell abnormalities. |
| How does damage to the cell's nucleus reveal itself? | Instant death, reproductive death, apoptosis, mitotic or genetic death, mitotic delay, and interference with function |
| True or False: cells vary in their radiosensitivity | True |
| What is the cell survival curve? | Displays the sensitivity of a particular type of cell to radiation. It is constructed from data obtained by a series of experiments. |
| Which cells are radiosensitive? | Basal cells of the skin, blood cells such as lymphocytes and erythrocytes, intestinal crypt cells, reproductive cells, brain cells, muscle cells, and nerve cells |
| True or False: As LET increases, the ability of the radiation to cause biologic effects also generally increases until it reaches a maximal value | True |
| True or False: LET cannot influence cell radiosensitivity | False; it can |
| True or False: Oxygen enhances the effects of ionizing radiation on biologic tissue by increasing tissue radiosensitivity | True |
| True or False: In radiotherapy, when radiation is used to treat certain types of cancerous tumors, high-pressure oxygen has sometimes been used in conjunction with it to increase tumor radiosensitivity | True |
| What is the Law of Bergoine and Tribondeau? | The radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation |
| True or False: Equal doses of ionizing radiation produce different degrees of damage in different kinds of human cells because of differences in cell radiosensitivity | True |
| What are the effects of ionizing radiation on blood cells? | Hematologic depression, depletion of immature blood cells, repopulation after a period of recovery, effects on stem cells of the hematopoietic system, whole-body doses in excess of 5 Gyt, etc. |
| What are early effects? | Biologic effects of radiation that occur relatively soon after humans receive high doses of ionizing radiation and is not common in diagnostic imaging |
| What are somatic effects? | Effects upon the body that was irradiated |
| What are genetic effects? | Effects upon future generations because of irradiation of germ cells in previous generations |
| True or False: the effects are classified as either early somatic effects or late somatic effects | True |
| True or False: Early tissue reactions have a threshold and the amount of biologic damage depends on the actual absorbed dose of ionizing radiation | True |
| How early do these reactions appear? | Within minutes, hours, days, or weeks of the time of radiation exposure |
| What are examples of high-dose effects? | Nausea, fatigue, erythema, epilation, blood disorders, intestinal disorders, fever, dry and moist desquamation, depressed sperm count in the male, etc. |
| What is Acute Radiation Syndrome? | Aka radiation sickness; occurs in humans after whole-body reception of large doses of ionizing radiation delivered over a short period of time |
| What is hematopoietic syndrome? | Aka bone marrow syndrome; from 1-10 Gyt |
| What is gastrointestinal syndrome? | Appears at a threshold dose of approximately 6 Gyt and peaks after a dose of 10 Gyt |
| What is cerebrovascular syndrome? | Results from doses of 50 Gyt or more |
| What are the four major response stages in ARS? | Prodromal (initial stage), latent period, manifest illness, and recovery or death |
| What is a lethal dose? | LD 50/30 which signifies the whole body dose of radiation that can be lethal to 50% of the exposed population within 30 days |
| True or False: cells that are more oxygenated receive more nutrients, having a better prospect for recovery than do hypoxic cells | True |
| True or False: if recovery occurs, it may be partial or complete, depending on the type of cells involved and the dose of radiation receieved | True |
| True or False: If organ and tissue recovery fails to occur, necrosis or death of the irradiated biologic structure results | True |
| Organ and tissue response to radiation exposure depends on | Radiosensitivity, reproductive characteristics, and growth rate |
| What is epilation? | Aka hairloss from moderate-large doses of radiation |
| What is cytogenetics? | Study of cell genetics with emphasis on cell chromosomes |
| What is a karyotype? | Map consists of a photograph or photomicrograph |
| What is a metaphase? | Phase of cell division where the chromosome damage caused by radiation exposure can be evaluated. Chromosome aberrations and chromatid aberrations are observed at this phase. |
| What are late effects? | Radiation-induced damage at the cellular level may lead to measurable somatic and hereditary damage in the living organism as a whole in later life. The long-term results of radiation exposure |
| Examples of late biologic damage? | Cataracts, Leukemia, Genetic mutations |
| What is epidemiology? | Science that deals with the incidence, distribution, and control of disease in a population |
| What is carcinogenesis? | Aka tumorigenesis; formation of cancer |
| What is the radiation dose-response relationship? | A curve that maps the observed effects of radiation exposure in relation to the dose of radiation receieved |
| What is a threshold? | A point at which a response or reaction to an increasing stimulation first occurs. Below a certain radiation level or dose, no biologic effects are observed |
| What is nonthreshold? | Radiation absorbed dose of any magnitude has the capability of producing a biologic effect. No radiation dose can be absolutely safe with the severity of the biologic effects increasing directly with the magnitude of absorbed dose |
| What is the LNT curve? | Implies that the biologic response to ionizing radiation is directly proportional to the dose received |
| What is the sigmoid or S-shaped threshold curve? | Generally in radiation therapy to demonstrate high-dose cellular response to the radiation absorbed within specific locations |
| What are late somatic effects? | Consequences of radiation exposure that appear months or years after exposure |
| What are major types of late effects? | Carcinogenesis, cataractogenesis, and embryologic effects |
| True or False: at high doses, the risk is measurable in exposed human populations | True |
| True or False: at low doses, the risk is not directly measurable in population studies since the risk is overshadowed by other causes of cancer and the risk is zero | True |
| What do absolute risk and relative risk predict? | The number of excess cancers, or cancers that would not have occurred in the population in question without the exposure to ionizing radiation |
| Why do imaging professionals need to be familiar with previous, existing, and new guidelines for radiation safety? | They share the responsibility for patient safety from radiation exposure and are subject to radiation exposure in the performance of their duties |
| What does the international commission on radiological protection do? | International authority on the safe use of ionizing radiation, provides recommendations for occupational dose limits and public dose limits |
| What does the United Nations Scientific Committee on the Effects of Atomic Radiation evaluate? | Evaluates human and environmental ionizing radiation exposures including radioactive materials, radiation-producing machines, and radiation accidents |
| What does the MAS/NCR-BEIR do? | Reviews studies of biologic effects of ionizing radiation and risk assessment |
| What does the Radiation Safety Committee do? | Provide guidance for the program, facilitates ongoing operation of the program, and selects a qualified person to serve as a radiation safety officer |
| What should an RSO do? | Develop the radiation safety program, ensure the facility's radiation practices are adequate, implement and enforce policies of the program, and review and maintain records |
| What is the CDRH responsible for? | Conducting an ongoing electronic product radiation control program |
| ALARA is also known as? | Optimization |
| What is the EfD Limiting System? | Method for controlling risk of biologic damage to radiation workers and the general public |
| What is the tissue weighting factor? | Indicates the ratio of the risk of stochastic effects attributable to irradiation of a given organ or tissue to the total risk when the body is uniformly irradiated |
| What is the cumulative EfD limit? | A radiation worker's lifetime EfD must be limited to his or her age in years times 10 mSv and does not include radiation exposure from natural background radiation; includes internal and external exposure |
| What does the NCRP recommend as the monthly EqD limit per month to the embryo and entire pregnancy? | Embryo-fetus limit not exceeding 0.5 mSv and entire pregnancy not to exceed 5.0 mSv |
| What is the limit to the crystalline lens of the eye? | 150 mSv |
| What is the limit for localized areas of the skin, such as the hands and feet? | 500 mSv |
| What is radiation hormesis? | Concept that there exists a beneficial aspect or result to groups of individuals from continuing exposure to small amounts of radiation |
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